In recent years, as a storage system for efficiently operating storage areas in a simple configuration, a storage system which includes a storage system for providing dynamically expandable dynamic logical volumes, a host computer with file systems for inputting/outputting data to/from the dynamic logical volumes, and a management server for managing the storage system and the host computer has been proposed, for example (See PTL1, for example).
The storage system in the foregoing storage system is configured comprising an allocation part for allocating storage areas in predetermined units to the dynamic logical volumes when data, transmitted from the host computer, is stored in the dynamic logical volumes, a management part for managing the storage areas, among the storage areas allocated by the allocation part to the dynamic logical volumes, which are identified as being currently used by the file systems, and a release part for releasing storage areas not being managed by the management part from the dynamic logical volumes.
With the foregoing storage system, storage areas can be efficiently operated using a simple configuration as a result of the storage system allocating storage areas to the dynamic logical volumes in predetermined units when data transmitted from the host computer is stored in the dynamic logical volumes, managing the storage areas, among the storage areas allocated to the dynamic logical volumes, which are identified as currently in use by the file systems, and releasing unmanaged storage areas from the dynamic logical volumes, the storage system thereby releasing unnecessary storage area from the dynamic logical volumes without ascertaining the structure of the file systems.
However, in the foregoing storage system, no consideration is paid to performing effective data migration by way of co-operation between the storage system and the file systems.
Furthermore, network storage (Network Attached Storage) in which a storage system is connected to a network and used as a shared disk of computers connected to the network has been proposed. The network storage (NAS) is configured from a server which comprises a network interface and so on, and a disk drive for storing data.
If a file system or part of a file system is migrated in NAS with a cluster structure that includes a server, file data must be copied between each of the disk devices of each server. In this case, when there is a large volume of data, it takes time to copy the file data and client file access performance may deteriorate.
For this reason, an arrangement has been proposed whereby, in a storage system which comprises a plurality of servers, file systems or partial directory trees thereof are migrated without being copied (See PTL2).
In the system disclosed in PTL2, a configuration is adopted such that the plurality of servers comprise a management table for managing file systems or part thereof and a mapping table for managing relationships between logical devices of disk subsystems and logical units which recognize the servers, and, when a file system is migrated from a first server to a second server of the plurality of servers, the first server refers to the mapping table and transmits a direction to the second server to update the relationships between the logical devices and logical units, and the second server recognizes new logical units and updates management server identifiers in the management table.